Chick-provisioning behaviour of two shearwaters breeding in south-eastern Australia.

AbstractThe chick-provisioning behaviour of the short-tailed shearwater Puffinus tenuirostris and the wedge-tailed shearwater Puffinus pacificus was investigated in a mixed colony on Montague Island, New South Wales, Australia, over two breeding seasons. This colony is located at opposite edges of the breeding distribution of the two species. Frequent weighing techniques were used to determine chick feeding frequency, feed timing, meal size, chick weight loss and indices of food conversion efficiency of the chicks. Short-tailed shearwater parents fed their chicks larger more infrequent meals than wedge-tailed shearwater parents. Short-tailed shearwater chicks demonstrated higher food conversion efficiencies and lower weight loss than wedge-tailed shearwater chicks, indicating either differences in diet or metabolic rates. The feeding frequency in wedge-tailed shearwaters also fluctuated more widely than for short-tailed shearwaters over the two breeding seasons. Despite the fact that the timing of the breeding cycle on Montague Island is almost identical for the two species, these differences in chick provisioning are probably a result of differences in prey type and location, so they may help explain variations in annual breeding success and limits to the distribution of the two species. [ABSTRACT FROM AUTHOR]